Induce Neutralizing Antibodies Research Articles

COVID-19 vaccine induced poor neutralization titers for SARS-CoV-2 omicron variants in maternal and cord blood.

Maternally derived antibodies are crucial for neonatal immunity. Understanding the binding and cross-neutralization capacity of maternal and cord antibody responses to SARS-CoV-2 variants following COVID-19 vaccination in pregnancy can inform neonatal immunity. Here we characterized the binding and neutralizing antibody profile at delivery in 24 pregnant individuals following two doses of Moderna mRNA-1273 or Pfizer BNT162b2 vaccination. We analyzed for SARS-CoV-2 multivariant cross-neutralizing antibody levels for wildtype Wuhan, Delta, Omicron BA1, BA2, and BA4/BA5 variants. In addition, we evaluated the transplacental antibody transfer by profiling maternal and umbilical cord blood. Our results reveal that the current COVID-19 vaccination induced significantly higher RBD-specific binding IgG titers in cord blood compared to maternal blood for both the Wuhan and Omicron BA1 strain. Interestingly, the binding IgG antibody levels for the Omicron BA1 strain were significantly lower when compared to the Wuhan strain in both maternal and cord blood. In contrast to the binding, the Omicron BA1, BA2, and BA4/5 specific neutralizing antibody levels were significantly lower compared to the Wuhan and Delta variants. It is interesting to note that the BA4/5 neutralizing capacity was not detected in either maternal or cord blood. Our data suggest that the initial series of COVID-19 mRNA vaccines were immunogenic in pregnant women, and vaccine-elicited binding antibodies were detectable in cord blood at significantly higher levels for the Wuhan and Delta variants but not for the Omicron variants. Interestingly, the vaccination did not induce neutralizing antibodies for Omicron variants. These results provide novel insight into the impact of vaccination on maternal humoral immune response and transplacental antibody transfer for SARS-CoV-2 variants and support the need for bivalent boosters as new variants emerge.

Inactivated SARS-CoV-2 vaccine candidate immunization on non-human primate animal model: B-cell and T-cell responses immune evaluation

BackgroundSARS-CoV-2 vaccine was proven to be an effective and efficient measure for mitigating pandemic. COVID-19 infection and mortality subsided along with the increaseing COVID-19 vaccination coverage. Vaccine and health resource equity are predominant factors in COVID-19 pandemic management. Vaccine development for Indonesia, aims to ensure a sustainable pandemic control and steady national stability restoration. A decent vaccine must induce immunity against COVID-19 with minimum adverse reaction. Immunogenicity and ability to induce neutralizing antibody evaluation needs to be performed as part of the SARS-CoV-2 inactivated vaccine development from East Java, Indonesia isolate (Vaksin Merah Putih-INAVAC). ObjectiveThis research demonstrated INAVAC performance in inducing the production neutralizing antibody along with its effects on CD4+ and CD8+ cells response in Macaca fascicularis (non-human primate). MethodsTwo dosages of 3 μg and 5 μg were tested, compared to sham (NaCl 0.9%) in 10 Macaca fascicularis (2 injection intramuscular with 14 days interval). All animals were monitored daily for clinical signs. Nasopharyngeal samples were analyzed using qRT-PCR while the serum were tested using ELISA and neutralization assay, whereas PBMCs were flowcytrometrically analyzed to measure CD4+ and CD8+ population. ResultsIt is observed that both vaccine doses could stimulate relatively similar immune response and neutralizing antibody (end GMT post challenge = 905,1), whereas higher CD8+ cells response were reported in the 5 μg group after the 3rd day post-challenge. The dose of vaccine that produce adequate immune cell stimulation with neutralizing antibody induction can be adopted to clinical study, as favorable result of these parameters could predict minimum adverse reaction from inflammation response with balanced immune response. ConclusionsTherefore, it is concluded that Vaksin Merah Putih-INAVAC with 3 μg dose showed a favorable potential to be developed and tested as human vaccine.

Antisera Produced Using an E. coli-Expressed SARS-CoV-2 RBD and Complemented with a Minimal Dose of Mammalian-Cell-Expressed S1 Subunit of the Spike Protein Exhibits Improved Neutralization

E. coli-expressed proteins could provide a rapid, cost-effective, and safe antigen for subunit vaccines, provided we can produce them in a properly folded form inducing neutralizing antibodies. Here, we use an E. coli-expressed SARS-CoV-2 receptor-binding domain (RBD) of the spike protein as a model to examine whether it yields neutralizing antisera with effects comparable to those generated by the S1 subunit of the spike protein (S1 or S1 subunit, thereafter) expressed in mammalian cells. We immunized 5-week-old Jcl-ICR female mice by injecting RBD (30 µg) and S1 subunit (5 µg) according to four schemes: two injections 8 weeks apart with RBD (RBD/RBD), two injections with S1 (S1/S1), one injection with RBD, and the second one with S1 (RBD/S1), and vice versa (S1/RBD). Ten weeks after the first injection (two weeks after the second injection), all combinations induced a strong immune response with IgG titer > 105 (S1/RBD < S1/S1 < RBD/S1 < RBD/RBD). In addition, the neutralization effect of the antisera ranked as S1/RBD~RBD/S1 (80%) > S1/S1 (56%) > RBD/RBD (42%). These results indicate that two injections with E. coli-expressed RBD, or mammalian-cell-produced spike S1 subunit alone, can provide some protection against SARS-CoV-2, but a mixed injection scheme yields significantly higher protection.

Three neutralizing mAbs induced by MPXV A29L protein recognizing different epitopes act synergistically against orthopoxvirus

ABSTRACT The worldwide outbreak of the monkeypox virus (MPXV) has become a “Public Health Emergency of International Concern” (PHEIC). Severe monkeypox virus infection can be fatal, however, effective therapeutic methods are yet to be developed. Mice were immunized with A35R protein and A29L protein of MPXV, and the binding and neutralizing activities of the immune sera against poxvirus-associated antigens and viruses were identified. A29L protein and A35R protein-specific monoclonal antibodies (mAbs) were generated and their antiviral activities of these mAbs were characterized in vitro and in vivo. Immunization with the MPXV A29L protein and A35R protein induced neutralizing antibodies against the orthopoxvirus in mice. None of the mAbs screened in this study against A35R could effectively neutralize the vaccinia virus (VACV), while three mAbs against A29L protein, 9F8, 3A1 and 2D1 were confirmed to have strong broad binding and neutralizing activities against orthopoxvirus, among which 9F8 showed the best neutralizing activity. 9F8, 3A1, and 2D1 recognized different epitopes on MPXV A29L protein, showing synergistic antiviral activity in vitro against the VACV Tian Tan and WR strains; the best activity was observed when the three antibodies were combined. In the vivo antiviral prophylactic and therapeutic experiments, 9F8 showed complete protective activity, whereas 3A1 and 2D1 showed partial protective activity. Similarly, the three antibodies showed synergistic antiviral protective activity against the two VACVs. In conclusion, three mAbs recognized different epitopes on MPXV A29L protein were developed and showed synergistic effects against orthopoxvirus.

Increased Vaccination Diversity Leads to Higher and Less-Variable Neutralization of TBE Viruses of the European Subtype.

Tick-borne encephalitis (TBE) is an infectious disease of the central nervous system. The causative agent is the tick-borne encephalitis virus (TBEV), which is most commonly transmitted by tick bites, but which may also be transmitted through the consumption of raw dairy products or, in rare instances, via infected transfusions, transplants, or the slaughter of infected animals. The only effective preventive option is active immunization. Currently, two vaccines are available in Europe-Encepur® and FSME-IMMUN®. In Central, Eastern, and Northern Europe, isolated TBEV genotypes belong mainly to the European subtype (TBEV-EU). In this study, we investigated the ability of these two vaccines to induce neutralizing antibodies against a panel of diverse natural TBEV-EU isolates from TBE-endemic areas in southern Germany and in regions of neighboring countries. Sera of 33 donors vaccinated with either FSME-IMMUN®, Encepur®, or a mixture of both were tested against 16 TBEV-EU strains. Phylogenetic analysis of the TBEV-EU genomes revealed substantial genetic diversity and ancestry of the identified 13 genotypic clades. Although all sera were able to neutralize the TBEV-EU strains, there were significant differences among the various vaccination groups. The neutralization assays revealed that the vaccination using the two different vaccine brands significantly increased neutralization titers, decreased intra-serum variance, and reduced the inter-virus variation.

Epidemiological and Genetic Analysis of Foot-and-Mouth Disease Virus O/ME-SA/Ind-2001 in China between 2017 and 2021

The O/ME-SA/Ind-2001 lineage of foot-and-mouth disease virus (FMDV) was introduced into China in 2017, which subsequently caused 19 outbreaks of foot-and-mouth disease (FMD) and emerged in 8 provinces in China between 2017 and 2021. It is the first time for WOAH/national reference laboratory for FMD (LVRI) to comprehensively summarize these 19 outbreaks of O/ME-SA/Ind-2001 for consecutive 5 years. Our study selected and conducted whole viral genome sequencing for 9 representative isolates and the VP1 sequences of the FMDV-positive samples collected between 2017 and 2021. Analyses of these gene sequences showed that all the field strains belonged to O/ME-SA/Ind-2001e. Phylogenetic analysis indicated that these viruses were closely related to those circulating in neighboring countries, and there were at least 3 different FMD viral clades (named cluster 1, cluster 2, and cluster 3) circulating during this period. Also, a gradually decreasing nucleotide identity was observed in newly emerging viruses year by year compared with the first isolate identified in 2017. These results suggest extensive movements and constant and rapid evolvement of the O/ME-SA/Ind-2001e sublineage. Besides, the neutralizing antigenic sites in the structural proteins for these O/ME-SA/Ind-2001e viruses were analyzed to predict the vaccine matching between these strains and the commercial vaccine strain O/BY/CHA/2010. The results showed that the VP1 epitope 135–144, highly associated with neutralizing antibody induction, was variable among these strains. The mutations in this region reflected a potential risk of challenging the current vaccine protection. Therefore, there is an urgent need to reinforce the importance of improved FMD surveillance and monitor the evolution of O/ME-SA/Ind-2001e, which will provide essential information for the FMD control program in China and Asia.

Identification and Analysis of Monoclonal Antibodies with Neutralizing Activity against Diverse SARS-CoV-2 Variants.

We identified neutralizing monoclonal antibodies against severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) variants (including Omicron variants BA.5 and BA.2.75) from individuals who received two doses of mRNA vaccination after they had been infected with the D614G virus. We named them MO1, MO2, and MO3. Among them, MO1 showed particularly high neutralizing activity against authentic variants: D614G, Delta, BA.1, BA.1.1, BA.2, BA.2.75, and BA.5. Furthermore, MO1 suppressed BA.5 infection in hamsters. A structural analysis revealed that MO1 binds to the conserved epitope of seven variants, including Omicron variants BA.5 and BA.2.75, in the receptor-binding domain of the spike protein. MO1 targets an epitope conserved among Omicron variants BA.1, BA.2, and BA.5 in a unique binding mode. Our findings confirm that D614G-derived vaccination can induce neutralizing antibodies that recognize the epitopes conserved among the SARS-CoV-2 variants. IMPORTANCE Omicron variants of SARS-CoV-2 acquired escape ability from host immunity and authorized antibody therapeutics and thereby have been spreading worldwide. We reported that patients infected with an early SARS-CoV-2 variant, D614G, and who received subsequent two-dose mRNA vaccination have high neutralizing antibody titer against Omicron lineages. It was speculated that the patients have neutralizing antibodies broadly effective against SARS-CoV-2 variants by targeting common epitopes. Here, we explored human monoclonal antibodies from B cells of the patients. One of the monoclonal antibodies, named MO1, showed high potency against broad SARS-CoV-2 variants including BA.2.75 and BA.5 variants. The results prove that monoclonal antibodies that have common neutralizing epitopes among several Omicrons were produced in patients infected with D614G and who received mRNA vaccination.

Adjuvant skewing of host immune response to vaccination and subsequent infection with influenza virus

Abstract Despite being a vaccine-preventable disease, seasonal influenza is responsible for thousands of hospitalizations and deaths yearly. Currently licensed quadrivalent inactivated influenza virus vaccines (QIV) aim to induce neutralizing antibodies but are poor inducers of T-cell responses, which could be potentially overcome with adjuvants. We evaluated adjuvant skewing of host-immune responses after vaccination and its persistence after infection. Hereto, we compared two squalene-based adjuvants (AddaVax, and AddaS03) and IMDQ-PC, a lymph node-draining TLR7/8 agonist. All adjuvants resulted in enhanced antibody titers and protection against challenge with H1N1 influenza virus. Lung cytokine/chemokine profiling at 5 days post-infection showed that AddaVax results in higher levels of type 2 immunity-stimulating cytokines IL-4, -5, and -13 in the lungs, which is also reflected by a higher IgG1:IgG2a ratio. Meanwhile, IMDQ-PC showed higher serological IgG2a titers after vaccination and higher levels of IFNγ in the lungs after challenge. To investigate the role of the myeloid compartment in adjuvant skewing of host responses, we examined adjuvant-mediated skewing of bone-derived macrophages in-vitro using Arginase I and iNOS as M2 or M1 markers, respectively. We also pre-licensed macrophages with IL-4 and IFNγ to evaluate adjuvant-intrinsic skewing effects. Licensing was required to induce M1 or M2 phenotypes by squalene-based adjuvants, whereas IMDQ-PC skewed towards M1 phenotype irrespective of licensing. Correlating with the observed type I immune host response, IMDQ-PC induced iNOS more robustly with IFNγ than the other adjuvants. And, AddaS03 induced the highest levels of Arginase I in the IL-4 group. This study was also partly funded by CRIPT (Center for Research on Inuenza Pathogenesis and Transmission), a NIH NIAID funded Center of Excellence for Influenza Research and Response (CEIRR, contract number 75N93021C00014), by the NIAID funded SEM-CIVIC consortium to improve inuenza vaccines (contract number 75N93019C00051), to AG-S. By NIH/NIAID HHSN272201400008C (L.C.), and NIH/NIAID R21AI151229 and R01AI160706 (M.S.). B.G.D.G. acknowledges funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (grant N 817938).

Intrinsic B cell TLR-BCR linked coengagement induces class-switched, hypermutated, neutralizing antibody responses in absence of T cells.

Maturation of antibody responses entails somatic hypermutation (SHM), class-switch DNA recombination (CSR), plasma cell differentiation, and generation of memory B cells, and it is thought to require T cell help. We showed that B cell Toll-like receptor 4 (TLR4)-B cell receptor (BCR) (receptor for antigen) coengagement by 4-hydroxy-3-nitrophenyl acetyl (NP)-lipopolysaccharide (LPS) (Escherichia coli lipid A polysaccharide O-antigen) or TLR5-BCR coengagement by Salmonella flagellin induces mature antibody responses to NP and flagellin in Tcrβ-/-Tcrδ-/- and NSG/B mice. TLR-BCR coengagement required linkage of TLR and BCR ligands, "linked coengagement." This induced B cell CSR/SHM, germinal center-like differentiation, clonal expansion, intraconal diversification, plasma cell differentiation, and an anamnestic antibody response. In Tcrβ-/-Tcrδ-/- mice, linked coengagement of TLR4-BCR by LPS or TLR5-BCR by flagellin induced protective antibodies against E. coli or Salmonella Typhimurium. Our findings unveiled a critical role of B cell TLRs in inducing neutralizing antibody responses, including those to microbial pathogens, without T cell help.

Mpox multi-antigen mRNA vaccine candidates by a simplified manufacturing strategy afford efficient protection against lethal orthopoxvirus challenge

ABSTRACT Current unprecedented mpox outbreaks in non-endemic regions represent a global public health concern. Although two live-attenuated vaccinia virus (VACV)-based vaccines have been urgently approved for people at high risk for mpox, a safer and more effective vaccine that can be available for the general public is desperately needed. By utilizing a simplified manufacturing strategy of mixing DNA plasmids before transcription, we developed two multi-antigen mRNA vaccine candidates, which encode four (M1, A29, B6, A35, termed as Rmix4) or six (M1, H3, A29, E8, B6, A35, termed as Rmix6) mpox virus antigens. We demonstrated that those mpox multi-antigen mRNA vaccine candidates elicited similar potent cross-neutralizing immune responses against VACV, and compared to Rmix4, Rmix6 elicited significantly stronger cellular immune responses. Moreover, immunization with both vaccine candidates protected mice from the lethal VACV challenge. Investigation of B-cell receptor (BCR) repertoire elicited by mpox individual antigen demonstrated that the M1 antigen efficiently induced neutralizing antibody responses, and all neutralizing antibodies among the top 20 frequent antibodies appeared to target the same conformational epitope as 7D11, revealing potential vulnerability to viral immune evasion. Our findings suggest that Rmix4 and Rmix6 from a simplified manufacturing process are promising candidates to combat mpox.

Delayed generation of functional virus-specific circulating T follicular helper cells correlates with severe COVID-19

Effective humoral immune responses require well-orchestrated B and T follicular helper (Tfh) cell interactions. Whether these interactions are impaired and associated with COVID-19 disease severity is unclear. Here, longitudinal blood samples across COVID-19 disease severity are analysed. We find that during acute infection SARS-CoV-2-specific circulating Tfh (cTfh) cells expand with disease severity. SARS-CoV-2-specific cTfh cell frequencies correlate with plasmablast frequencies and SARS-CoV-2 antibody titers, avidity and neutralization. Furthermore, cTfh cells but not other memory CD4 T cells, from severe patients better induce plasmablast differentiation and antibody production compared to cTfh cells from mild patients. However, virus-specific cTfh cell development is delayed in patients that display or later develop severe disease compared to those with mild disease, which correlates with delayed induction of high-avidity neutralizing antibodies. Our study suggests that impaired generation of functional virus-specific cTfh cells delays high-quality antibody production at an early stage, potentially enabling progression to severe disease.

Mimotope discovery as a tool to design a vaccine against Zika and dengue viruses.

Vaccine development against dengue virus is challenging because of the antibody-dependent enhancement of infection (ADE), which causes severe disease. Consecutive infections by Zika (ZIKV) and/or dengue viruses (DENV), or vaccination can predispose to ADE. Current vaccines and vaccine candidates contain the complete envelope viral protein, with epitopes that can raise antibodies causing ADE. We used the envelope dimer epitope (EDE), which induces neutralizing antibodies that do not elicit ADE, to design a vaccine against both flaviviruses. However, EDE is a discontinuous quaternary epitope that cannot be isolated from the E protein without other epitopes. Utilizing phage display, we selected three peptides that mimic the EDE. Free mimotopes were disordered and did not elicit an immune response. After their display on adeno-associated virus (AAV) capsids (VLP), they recovered their structure and were recognized by an EDE-specific antibody. Characterization by cryo-EM and enzyme-linked immunosorbent assay confirmed the correct display of a mimotope on the surface of the AAV VLP and its recognition by the specific antibody. Immunization with the AAV VLP displaying one of the mimotopes induced antibodies that recognized ZIKV and DENV. This work provides the basis for developing a Zika and dengue virus vaccine candidate that will not induce ADE.

Successful liver transduction by re-administration of different adeno-associated virus vector serotypes in mice.

Intravenous administration of adeno-associated virus (AAV) vectors is a promising gene therapy approach for monogenic diseases. However, re-administration of the same AAV serotype is impossible because of the induction of anti-AAV neutralizing antibodies (NAbs). Here, we examined the feasibility of re-administrating AAV vector serotypes different from the initial AAV vector serotype. Liver-targeting AAV3B, AAV5, and AAV8 vectors were intravenously injected in C57BL/6 mice, and the emergence of NAbs and the transduction efficacy following re-administration were evaluated. For all serotypes, re-administration of the same serotype was not possible. Although the highest neutralizing activity of NAb was induced by AAV5, anti-AAV5 NAbs did not react with other serotypes, resulting in successful re-administration with the other serotypes. AAV5 re-administration was also successful in all mice treated with AAV3B and AAV8. Effective secondary administration of AAV3B and AAV8 was observed in most mice initially administrated AAV8 and AAV3B, respectively. However, few mice developed NAbs cross-reacting with the other serotypes, especially those with close sequence homology. In summary, AAV vector administration induced NAbs relatively specific to the administrated serotype. Secondary administration of AAVs targeting liver transduction could be successfully achieved by switching AAV serotypes in mice.

Induction of antitoxic antibody and preventive effect against porcine edema disease by the pentameric Stx2eB subunit vaccine

Porcine edema disease (ED) is an enterotoxaemia that frequently occurs in 4–12 week-old piglets and results in high mortality. ED is caused by Shiga toxin 2e (Stx2e), produced by host-adapted Shiga toxin-producing Escherichia coli (STEC) strains. We constructed a recombinant protein in which the B subunit of Stx2e (Stx2eB) was linked to Cartilage Oligomeric Matrix Protein (COMP)’s pentameric domain to enhance antigenicity to induce neutralizing antibodies against Stx2e. We evaluated the efficacy of this antigen as a vaccine on the farm where ED had occurred. The suckling piglets were divided into two groups. The pigs in the vaccinated group were intramuscularly immunized with the vaccine containing 30 µg/head of Stx2eB-COMP at 1 and 4 weeks of age. The control pigs were injected with saline instead of the vaccine. The neutralizing antibody titer to Stx2e, mortality, clinical score, and body weight was evaluated up to 11 weeks after the first vaccination. In the vaccinated group, the Stx2e neutralizing antibody was detected 3 weeks after the first vaccination, its titer increased during the following weeks. The antibody was not detected in the control group during the test period. The STEC gene was detected in both groups during the test period, but a typical ED was observed only in control pigs; the mortality and clinical score were significantly lower in the vaccinated group than in the control group. These data indicate that the pentameric B subunit vaccine is effective for preventing ED and offers a promising tool for pig health control.

Protection from SARS-CoV-2 Variants by MVAs expressing matched or mismatched S administered intranasally to mice

SARS-CoV-2 vaccines prevent severe disease but are less efficient in averting infection and transmission of variant strains, making it imperative to explore ways of enhancing protection. Use of inbred mice expressing the human SARS-CoV-2 receptor facilitates such investigations. We employed recombinant MVAs (rMVAs) expressing modified S of several SARS-CoV-2 strains and compared their ability to neutralize variants, bind S proteins and protect K18-hACE2 mice against SARS-CoV-2 challenge when administered intramuscularly or intranasally. The rMVAs expressing Wuhan, Beta and Delta S induced substantial cross neutralizing activities to each other but very low neutralization of Omicron; while rMVA expressing Omicon S induced neutralizing antibody predominanly to Omicron. In mice primed and boosted with rMVA expressing the Wuhan S, neutralizing antibodies to Wuhan increased after one immunization with rMVA expressing Omicron S due to original antigenic sin, but substantial neutralizing antibody to Omicron required a second immunization. Nevertheless, monovalent vaccines with S mismatched to the challenge virus still protected against severe disease and reduced the amounts of virus and subgenomic RNAs in the lungs and nasal turbinates, though not as well as vaccines with matched S. Passive transfer of Wuhan immune serum with Omicron S binding but undetectable neutralizing activity reduced infection of the l–ungs by Omicron suggesting additional effector functions. Notably, there was less infectious virus and viral subgenomic RNAs in the nasal turbinates and lungs when the rMVAs were administered intranasally rather than intramuscularly and this held true for vaccines that were matched or mismatched to the challenge strain of SARS-CoV-2.

Rational development of multicomponent mRNA vaccine candidates against mpox

ABSTRACT The re-emerging mpox (formerly monkeypox) virus (MPXV), a member of Orthopoxvirus genus together with variola virus (VARV) and vaccinia virus (VACV), has led to public health emergency of international concern since July 2022. Inspired by the unprecedent success of coronavirus disease 2019 (COVID-19) mRNA vaccines, the development of a safe and effective mRNA vaccine against MPXV is of high priority. Based on our established lipid nanoparticle (LNP)-encapsulated mRNA vaccine platform, we rationally constructed and prepared a panel of multicomponent MPXV vaccine candidates encoding different combinations of viral antigens including M1R, E8L, A29L, A35R, and B6R. In vitro and in vivo characterization demonstrated that two immunizations of all mRNA vaccine candidates elicit a robust antibody response as well as antigen-specific Th1-biased cellular response in mice. Importantly, the penta- and tetra-component vaccine candidates AR-MPXV5 and AR-MPXV4a showed superior capability of inducing neutralizing antibodies as well as of protecting from VACV challenge in mice. Our study provides critical insights to understand the protection mechanism of MPXV infection and direct evidence supporting further clinical development of these multicomponent mRNA vaccine candidates.

RSV A2-Based Prefusion F Vaccine Candidates Induce RSV A and RSV B Cross Binding and Neutralizing Antibodies and Provide Protection against RSV A and RSV B Challenge in Preclinical Models

RSV is divided into two antigenic subtypes, RSV A and RSV B, which is largely based on the variation in the G protein, while the fusion protein F is more conserved and a target for antibody-mediated neutralization. Here we evaluate the breadth of the protective immune responses across RSV A and RSV B subtypes, induced by vaccines based on the RSV A-based fusion protein, stabilized in the prefusion conformation (preF) in preclinical models. Immunization of naïve cotton rats with preF subunit or preF encoded by a replication incompetent Adenoviral 26, induced antibodies capable of neutralizing recent RSV A and RSV B clinical isolates, as well as protective efficacy against a challenge with RSV A and RSV B strains. Similarly, induction of cross-neutralizing antibodies was observed after immunization with Ad26-encoded preF, preF protein or a mix of both (Ad26/preF protein) in RSV pre-exposed mice and African Green Monkeys. Transfer of serum of human subjects immunized with Ad26/preF protein into cotton rats provide protection against challenges with both RSV A and RSV B, with complete protection against both strains observed in the lower respiratory tract. In contrast, almost no protection against RSV A and B infection was observed after the transfer of a human serum pool isolated pre-vaccination. These results collectively show that the RSV A-based monovalent Ad26/preF protein vaccine induced neutralizing antibodies, as well as protection against both RSV A and RSV B subtypes in animals, including by passive transfer of human antibodies alone, suggesting that clinical efficacy against both subtypes can be achieved.

CpG 1018 Is an Effective Adjuvant for Influenza Nucleoprotein.

Current influenza vaccines mainly induce neutralizing antibodies against the highly variable surface antigen hemagglutinin and require annual manufacturing and immunization. Different from surface antigens, intracellular nucleoprotein (NP) is highly conserved and has been an attractive target to develop universal T cell vaccines against influenza. Yet, influenza NP protein mainly induces humoral immune responses and lacks the ability to induce potent cytotoxic T lymphocyte (CTL) responses, key for the success of universal T cell vaccines. This study compared CpG 1018 and AddaVax to enhance recombinant NP-induced CTL responses and protection in murine models. CpG 1018 was explored to boost intradermal NP immunization, while AddaVax was explored to boost intramuscular NP immunization due to the high risk of AddaVax adjuvant to induce significant local reactions following intradermal delivery. We found CpG 1018 was highly effective to enhance NP-induced humoral and cellular immune responses superior to AddaVax adjuvant. Furthermore, CpG 1018 potentiated Th1-biased antibody responses, while AddaVax enhanced Th1/Th2-balanced antibody responses. CpG 1018 significantly enhanced IFNγ-secreting Th1 cells, while AddaVax adjuvant significantly increased IL4-secreting Th2 cells. Influenza NP immunization in the presence of CpG 1018 induced significant protection against lethal viral challenges, while influenza NP immunization in the presence of AddaVax failed to elicit significant protection. Our data validated CpG 1018 as an effective adjuvant to enhance influenza NP-induced CTL responses and protection.

Heterologous boost with mRNA vaccines against SARS-CoV-2 Delta/Omicron variants following an inactivated whole-virus vaccine

The coronavirus SARS-CoV-2 has mutated quickly and caused significant global damage. This study characterizes two mRNA vaccines ZSVG-02 (Delta) and ZSVG-02-O (Omicron BA.1), and associating heterologous prime-boost strategy following the prime of a most widely administrated inactivated whole-virus vaccine (BBIBP-CorV). The ZSVG-02-O induces neutralizing antibodies that effectively cross-react with Omicron subvariants. In naïve animals, ZSVG-02 or ZSVG-02-O induce humoral responses skewed to the vaccine's targeting strains, but cellular immune responses cross-react to all variants of concern (VOCs) tested. Following heterologous prime-boost regimes, animals present comparable neutralizing antibody levels and superior protection against Delta and Omicron BA.1variants. Single-boost only generated ancestral and omicron dual-responsive antibodies, probably by “recall” and “reshape” the prime immunity. New Omicron-specific antibody populations, however, appeared only following the second boost with ZSVG-02-O. Overall, our results support a heterologous boost with ZSVG-02-O, providing the best protection against current VOCs in inactivated virus vaccine–primed populations.

Porcine Reproductive and Respiratory Syndrome Virus Engineered by Serine Substitution on the 44th Amino Acid of GP5 Resulted in a Potential Vaccine Candidate with the Ability to Produce High Levels of Neutralizing Antibody

N-linked glycans covering GP5 neutralizing epitopes of porcine reproductive and respiratory syndrome virus (PRRSV) have been proposed to act as a sheath blocking the production of neutralizing antibodies. Herein, we genetically engineered PRRSV with serine (S) substitution on the 44th asparagine (N) on the GP5 ectodomain of PRRSV-2 lineage-1. To evaluate the recombinant PRRSV, in vivo experiments were performed in piglets. The recombinant virus group showed no viremia until 42 days post-inoculation (dpi), and the rectal temperature and average daily weight gain were in the normal range at the same time point as the negative control group. On the 42 dpi, both groups were challenged with the wild-type virus. The recombinant PRRSV group showed lower rectal temperature, viremia, and the lung lesions than that of the negative control group for 19 days post-challenge (dpc). Additionally, the recombinant virus induced 4.50 ± 3.00 (log2) and 8.25 ± 0.96 (log2) of neutralizing antibody before and after challenge, respectively. Taken together, this study confirmed that N44S substitution can create an infectious PRRSV that strongly induces neutralizing antibodies. In addition, the vCSL1-GP5-N44S mutant that we produced was confirmed to have potential as a vaccine candidate, showing good safety and protective effects in pigs.